Neuronopathic Gaucher disease (nGD) is caused by deleterious mutations in GBA1/Gba1 and the resultant defective activity of acid ?-glucosidase (GCase). nGD is a prototype lysosomal storage disease (LSD) that displays generalized neuronal death in central nerve system (CNS). Effective therapeutic interventions have had major effects on the CNS manifestations of nGD due to i) the inability of GCase to cross the blood brain barrier (BBB), ii) the rapid denaturation of GCase at serum pH, and iii) the inability f the membrane associated GCase expressed at wild-type levels in cells to be secreted in sufficient amounts for metabolic cross- correction. We identified two receptor-binding peptides (Rp) from apolipoprotein E that can facilitate protein delivery across the BBB and into many CNS cell types via the low-density lipoprotein receptor superfamily (LDLRf). Also, we demonstrated the therapeutic potential with CNS metabolic correction and concordant normalization of neurological deficits in an enzyme-deficient LSD murine model after long-term hematopoietic stem cells (HSC)-mediated gene therapy using a lentiviral vector (LV). Importantly, we show that carboxy terminal addition of the myc-tag to GCase does not alter the enzyme's structure, activity or stability. Moreover, we showed for the first time that megakaryocytes are capable of over-producing lysosomal enzymes and packaging them into platelets for cross-correction of enzyme-deficient cells. Finally, we developed viable nGD mouse models that mimic acute and chronic human nGD. Based on these strong preliminary data and the great unmet medical need for CNS therapy in nGD, we will test the hypothesis that fusion of Rp to GCase will enable the modified GCase to transcytose into the CNS with wide CNS cell distribution via the LDLRf, so that synergistic CNS benefits can be achieved from continuous production of GCase-Rp through protective depots, i.e., platelets and macrophages. The overall goal of the project is to develop a novel therapeutic approach utilizing LDLRf-mediated transcytosis for protein delivery across the BBB via LV- mediated gene transfer into HSC with lineage-restricted expression in protective depots for the treatment of the CNS manifestations and essential correction of the visceral disease in nGD. We will assess various GCase-Rp for LDLRf-mediated CNS delivery, develop lineage-restricted expression systems for sustained and targeted protein generation via protective depots, and evaluate protein bio-distribution and therapeutic benefits in nGD mouse models. This project aims at a major unmet medical need for efficient BBB transcytosis systems with broad distribution of the therapeutic macromolecules to many CNS cell types for the treatment of a wide variety of CNS diseases. The approaches developed in the studies have general and significant applicability to neurodegenerative diseases including other LSDs, and Parkinson and Alzheimer diseases.